Split from this thread:-
http://www.vintage-radio.net/forum/s...d.php?t=139659
There may be some inconsistencies.
I've been down this route, building a circuit replica of the two-transistor Arbiter Fuzz Face that Hendrix used (as a gift to my 32 year old amateur guitarist son).
But because Arbiter just shoved in any old germanium transistor they got their hands on, Hendrix bought them in quantities of 50 so he could select the very few that actually worked properly, and didn't keel over when the unit was used in hot conditions (ie when leakage shifted the bias condition enough).
For the deceptively simple circuit to work properly as originally designed, the transistors need to have a beta of 70 to 100 (most that I tested have a beta of much lower than that - 40-ish), and ideally to have a leakage of less than 100uA at 20C. And the reason that germanium, like the AC128, "sounds" better is because of their truly awful frequency response - hard fuzz doesn't have a hard biting edge.
I used a Peak DCA55 to select devices, because I'm always looking for an excuse to buy another interesting bit of test gear.
There are silicon versions out there with modified component values to try and tame the much higher beta and a peppering of capacitors to slow down the edges with hard fuzz. They sound pretty good, but very much not the same as the germanium versions. And like everything to do with musicians there are strong opinions out there on distortion pedals.
Craig